Studies of synchronized coronary venous retroperfusion (SRP) of acutely ischemic myocardium and development of new concepts of combined circulatory assist systems are proceeding. Synchronized retroperfusion appears to salvage ischemic tissue and exhibits myocardial metabolic improvements as well as reduction in systemic vascular resistance. A series of longer term experiments have been completed and confirm these benefits. Safety and effectiveness of SRP are studied further with microsphere perfusion measurements and detailed pathology assessment of treated hearts. A combination of SRP with intraaortic baloon pumping (IABP) was developed. It features a single synchronization and activation control. Initial study of this treatment following 1 hour coronary occlusion shows improved hemodynamics and metabolism relative to untreated controls. Further closed chest experimental investigation of such a circulatory assist is planned to determine the benefits to cardiac function, perfusion and viability of the jeopardized acutely ischemic myocardium. Acute augmentation of coronary collateral circulation is sought with an ascending aorta ballon pumping (AABP) concept for treating acute ischemia. The system is being developed and preliminary experiments indicate both feasibility and effective augmentation of diastolic aortic root pressure. The circulatory assist systems are being developed with a view to safe, expeditious and effective application in the clinical setting. The engineering of catheters is planned in conjunction with the Edwards Company of Santa Ana, California.